text: class Node(object):
      def __init__(self, value):
          self.value = value
          self.left = None
          self.right = None
  
  class BinaryTree(object):
      def __init__(self, root):
          self.root = Node(root)
  
      def search(self, find_val):
          """Return True if the value
          is in the tree, return
          False otherwise."""
          
          return self.preorder_search( self.root, find_val )
          
      
      def print_tree(self):
          """Print out all tree nodes
          as they are visited in
          a pre-order traversal."""
          current = self.root
          path = str()
          pre_orrder_traversal = self.preorder_print(current, path)
          return pre_orrder_traversal[:-1]
  
      def preorder_search(self, start, find_val):
          """Helper method - use this to create a 
          recursive search solution."""
          current = start
          
          if current != None:
              
              if find_val == current.value:
                  return True
              else:
                  return self.preorder_search( current.left, find_val) or self.preorder_search( current.right, find_val)
          else:        
              return False
  
      def preorder_print(self, start, traversal):
          """Helper method - use this to create a 
          recursive print solution."""
          
          if start != None:
              traversal += (str(start.value) + "-")
              traversal = self.preorder_print(start.left, traversal)
              traversal = self.preorder_print(start.right, traversal)
          return traversal
              
          
          
              
  
  # Set up tree
  tree = BinaryTree(1)
  tree.root.left = Node(2)
  tree.root.right = Node(3)
  tree.root.left.left = Node(4)
  tree.root.left.right = Node(5)
  
  # Test search
  # Should be True
  print( tree.search(4) )
  # Should be False
  print(  tree.search(6) )
  
  # Test print_tree
  # Should be 1-2-4-5-3
  print( tree.print_tree() )
  